Are people animals?
Some animals like tigers and alligators are dangerous to own. They are wild and lethal.
Some animals would go extinct if they were allowed to own them. A list of these animals can be found below.
Link26Endangered animal list
Certain dog breeds are aggressive and dangerous. Personality is a spectrum in dogs, some labradors have worse personalities than terriers. A list of these breeds will need to be added here in a spectrum from worst to best.
Some people say there should be a dangerous owner act as there is no such thing as a dangerous dog.
Link28History dangerous dog laws (U.K)
Ban dogs to clean up dog poo? http://www.bbc.co.uk/news/magazine-22853270